1. Field of the Invention
The present invention relates to novel glycyrrthetic acid derivatives, a process for the preparation thereof as well as an antiulcer agent comprising at least one of the derivatives, as an effective ingredient.
2. Related Arts
It has been known that glycyrrhetic acid and certain derivatives thereof have various pharmacological activities such as antidigestive ulcer, antiinflammatory, antiallergic and the like actions.
As compounds of this kind, for instance, following compounds have been proposed.
Carbenoxolone (U.S. Pat. No. 3070623);
Esters at 30-position of glycyrrhetic acid (U.S. Pat. No. 3070624);
Amine acid salt of glycyrrhetic acid (Jap. Examine Pat. Appln. Gazette No. 32798/1969);
Amides of Glycyrrhetic acid (Belgian Pat. No. 753773); and
Amides of 11-deoxoglycyrrhetic acid (BP 1346871).
The present inventors have proposed a novel synthetic method of 11-deoxoglycyrrhetic acid (Jap. Unexamined Pat. Appln. Gazette No. 70638/1984) and novel hemi-ester derivatives of 11-deoxoglycyrrhetic acid (Jap. Unexamined Pat. Appln. Gazette No. 8044/1983).
The glycyrrhetic acid and derivatives thereof have the useful pharmacological activities as referred to but show a disadvantage of that its administration shall cause an abnormality in electrolyte metabolism to bring a Na-accumulation and K-diuresis, an advanced stage of which results an appearance of a hypertension, hypocalcemia, edemia or the like symptom, so-called--Pseudoaldosteronism--.
Therefore, it is the actual circumstance that the use of glycyrrhetic acid or its derivative is highly restricted in dosage and giving period, in view of safety.